Communicating polarization-dependent information over a free space channel

ABSTRACT

Communicating polarization-dependent information over a free space channel may include separating a data signal carrying data into a first signal and a second signal each carrying a portion of the data of the data signal, modulating a first carrier signal with the first signal and a second carrier signal with the second signal, radiating the modulated first signal with a first polarization as a polarized first signal over a free space channel, radiating the modulated second signal with a second polarization as a polarized second signal over the free space channel, demodulating the polarized first signal and the polarized second signal, and combining the demodulated first signal with the demodulated second signal to provide an output signal carrying the data of the data signal.

BACKGROUND

As is well known, the Shannon-Hartley theorem is a foundational theoremof information theory. The Shannon-Hartley theorem addresses the maximumrate at which information can be transmitted over a communicationschannel based on a bandwidth of the channel and a signal-to-noise ratio(SNR) over the bandwidth (i.e., C=B log₂ (1+S/N), where C is channelcapacity, B is the bandwidth of the channel, S is signal power, and N isnoise power (i.e., S/N is the SNR).

As such, according to the Shannon-Hartley theorem, an increase inchannel capacity must be accompanied with an increase in either thebandwidth or the SNR. Conventional methods of increasing channelcapacity have attempted to use bandwidth and/or SNR, however, bandwidthis becoming increasingly limited and attempts to increase the SNR havealso proven difficult.

SUMMARY

Communicating polarization-dependent information may include separatinga data signal carrying data into two signals with each of the signalsholding a portion of the data. Modulation techniques may be applied totransmit the signals over a free space channel where each of the signalshas a polarization that is orthogonal to one another. This allows bothof the signals to radiate over the free space channel in the samefrequency spectrum without interfering with one another. As such, thecapacity of the channel may be increased without resorting to increasingthe bandwidth or the SNR and more information may be communicated overthe free space channel compared to conventional methods.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate various example systems, methods,and so on, that illustrate various example embodiments of aspects of theinvention. It will be appreciated that the illustrated elementboundaries (e.g., boxes, groups of boxes, or other shapes) in thefigures represent one example of the boundaries. One of ordinary skillin the art will appreciate that one element may be designed as multipleelements or that multiple elements may be designed as one element. Anelement shown as an internal component of another element may beimplemented as an external component and vice versa. Furthermore,elements may not be drawn to scale.

FIG. 1 illustrates a block diagram of an exemplary embodiment of a datacommunicator for communicating a data stream through free space withdifferently polarized electromagnetic radiation over a free spacechannel.

FIG. 2 illustrates a block diagram of another exemplary embodiment of adata communicator for communicating a data stream through free spacewith differently polarized electromagnetic radiation over a free spacechannel.

FIG. 3 illustrates a block diagram of another exemplary embodiment of adata communicator for communicating a data stream through free spacewith differently polarized electromagnetic radiation over a free spacechannel.

FIG. 3A illustrates a flow diagram for an exemplary method for decodinga synchronization signal.

FIG. 3B illustrates a flow diagram for an exemplary method 310 fordetecting and decoding a synchronization signal.

FIG. 3C illustrates a flow diagram of an exemplary method for correctinghorizontal polarization and vertical polarization via polarizationcorrection techniques.

FIG. 4 illustrates a block diagram of another exemplary embodiment of adata communicator for communicating a data stream through free spacewith differently polarized electromagnetic radiation over a free spacechannel.

FIG. 5 illustrates a flow diagram for an exemplary method forcommunicating a data stream through free space with differentlypolarized electromagnetic radiation over a free space channel.

FIG. 6 illustrates a block diagram of an exemplary machine forcommunicating a data stream through free space with differentlypolarized electromagnetic radiation.

DETAILED DESCRIPTION

The techniques presented herein may communicate a data stream throughfree space with differently polarized electromagnetic radiation over afree space channel. Key parts include separating the data stream into afirst portion and a second portion and communicating the first portionof the data stream with electromagnetic radiation having a firstpolarization and communicating the second portion of the data streamwith electromagnetic radiation having a second polarization differentthan the first polarization over the free space channel.

Once this is accomplished, the first portion of the data streamcommunicated with the electromagnetic radiation having the firstpolarization and the second portion of the data stream communicated withthe electromagnetic radiation having the second polarization may becommunicated over the free space channel without interfering with oneanother and with the bandwidth occupied by the spectrum of thetransmitted free space RF signal being less than the bandwidth requiredby conventional modulation techniques.(i.e., a bandwidth of the firstportion of the data stream communicated with the electromagneticradiation having the first polarization plus the bandwidth of the secondportion of the data stream communicated with the electromagneticradiation having the second polarization together greater than thetransmitted RF bandwidth.

Data contained in the first portion of the data stream communicated withthe electromagnetic radiation having the first polarization and datacontained in the second portion of the data stream communicated with theelectromagnetic radiation having the second polarization may beextracted and recombined to output the data stream.

FIG. 1 illustrates a block diagram of an exemplary embodiment of a datacommunicator 10 for communicating a data stream through free space withdifferently polarized electromagnetic radiation over a free spacechannel. To increase an amount of data of a data stream communicatedover a free space channel, the data communicator 10 may communicateportions of the data of the data stream with different polarizationsover the free space channel.

In the example of FIG. 1 , the data communicator 10 may receive a datasignal including a data stream, separate the data stream into a firstdata stream carrying an initial portion of the data stream and a seconddata stream carrying the remaining portion of the data stream, modulatethe first data stream onto a first radio frequency (RF) signal, modulatethe second data stream onto a second radio frequency (RF) signal,communicate the first RF signal with a first polarization, communicatethe second RF signal with a second polarization, extract the initialportion of the data stream from the first RF signal having the firstpolarization, extract the remaining portion of the data stream from thesecond RF signal having the second polarization, and recombine theinitial portion of the data stream and the remaining portion of the datastream into an output data stream. While the electromagnetic radiationdescribed in the example of FIG. 1 is RF radiation, the techniquesdescribed herein may be applied to any suitable electromagneticradiation.

The data communicator 10 may include a data source 12, a data separator14, a signal generator 16, a first modulator 18, a second modulator 20,a first transmitter 22, a second transmitter 24, a first receiver 26, asecond receiver 28, a demodulator 30, and an output source 32.

The data source 12 may provide an input signal 34 carrying a data streamhaving a first bandwidth to the data separator 14. The data separator 14may separate the input signal 34 into a first signal 36 carrying a firstportion of data of the data stream having a second bandwidth and asecond signal 38 carrying a second portion of data of the data streamhaving a third bandwidth. The first bandwidth of the input signal 34 maybe greater than each of the second bandwidth of the first signal 36 andthe third bandwidth of the second signal 38. In some implementations,the first portion of data of the data stream may be an initial portionand the second portion of data of the data stream may be a remainingportion such that the entire data stream is communicated by, at least inpart, the first signal 36 and the second signal 38.

The signal generator 16 may generate an RF carrier signal 40 which maybe fed to the first modulator 18 and the second modulator 20 as a firstRF carrier signal 40 a and a second RF carrier signal 40 b,respectively. However, the first RF carrier signal 40 a and the secondRF carrier signal 40 b may be the same or different signals.

The first RF carrier signal 40 a may be fed as an input to the firstmodulator 18 and the second RF carrier signal 40 b may be fed as aninput to the second modulator 20. The first modulator 18 may modulatethe first signal 36 onto the first RF carrier signal 40 a and output amodulated first RF signal 44. The second modulator 20 may modulate thesecond signal 38 onto the second RF carrier signal 40 b and output amodulated second RF signal 46.

The modulated first RF signal 44 may be fed as an input to the firsttransmitter 22 and the modulated second RF signal 46 may be fed as aninput to the second transmitter 24. The first transmitter 22 maytransmit the modulated first RF signal 44 with a first polarization overa free space channel 48. The second transmitter 24 may transmit themodulated second RF signal 46 with a second polarization that isdifferent than the first polarization through the free space channel 48.In some implementations, the first polarization may be horizontal andthe second polarization may be vertical, however, the first polarizationand the second polarization may be any suitable polarizations.

The first receiver 26 may receive the transmitted modulated first RFsignal 44 having the first polarization and output a received modulatedfirst RF signal 50. The second receiver 28 may receive the transmittedmodulated second RF signal 46 having the second polarization and outputa received modulated second RF signal 52. In some implementations, thefirst receiver 26 may be horizontally polarized and the second receiver28 may be vertically polarized, however, the first receiver 26 and thesecond receiver 28 may be polarized in any suitable manner.

The received modulated first RF signal 50 and the received modulatedsecond RF signal 52 may be fed as inputs to the demodulator 30. Thedemodulator 30 may demodulate the received modulated first RF signal 50and the received modulated second RF signal 52 to extract the firstportion of data of the data stream from the received modulated first RFsignal 50 and the second portion of data of the data stream from thereceived modulated second RF signal 52. The demodulator 30 may include acombiner 30 a that combines the first portion of data of the data streamextracted from the received modulated first RF signal 50 and the secondportion of the data of the data stream extracted from the receivedmodulated second RF signal 52 to output an output signal 54 carrying thedata stream that was contained in the input signal 34. The output signal54 may be fed as an input to the output source 32.

As such, one exemplary benefit of the data communicator 10 described inFIG. 1 is an increase in a channel capacity of the free space channel 48based, at least in part, on communicating portions of the data streamwith different polarizations such that there is no interference betweenthe communicated portions and no increase in the total bandwidth neededto communicate the data through the free space channel 48.

FIG. 2 illustrates a block diagram of another exemplary embodiment of adata communicator 200 for communicating a data stream through free spacewith differently polarized electromagnetic radiation over a free spacechannel. The data communicator 200 of FIG. 2 is substantially identicalto the data communicator 10 of FIG. 1 , with a few exceptions/changes asfurther described below.

More particularly, the data communicator 200 may include asynchronization signal controller 56, a synchronization signal decoder58, a first polarization corrector 60, and a second polarizationcorrector 62. The synchronization signal controller 56 may be inoperative communication with a first switch 56 a and a second switch 56b.

In some implementations, the polarization of the first transmitter 22may not match the polarization of the first receiver 26 and/or thepolarization of the second transmitter 24 may not match the polarizationof the second receiver 28. The received modulated first RF signal 50 maycarry both a first signal portion transmitted by the first transmitter22 and a second signal portion transmitted by the second transmitter 24mixed together in unequal portions. The received modulated second RFsignal 52 may carry both the first signal portion transmitted bytransmitter 22 and the second signal portion transmitted by the secondtransmitter 24 mixed together in unequal portions different from thereceived modulated first RF signal 50.

In these scenarios, axis rotation may be utilized to correct the spatialpolarization mismatch of the transmitted modulated first RF signal 44and the transmitted modulated second RF signal 46 with the firstreceiver 26 and second receiver 28, respectively. For example, thereceived modulated first RF signal 50 and the received modulated secondRF signal 52 may be corrected, via the first polarization corrector 60and the second polarization corrector 62, such that a correctedmodulated first RF signal 64 and a corrected modulated second RF signal66 each represents only one, or substantially one, type of polarizationbefore being fed as an input to the demodulator 30.

Stated otherwise, the corrected modulated first RF signal 64 may includethe first signal portion of the received modulated first RF signal 50and at least a part of the second signal portion of the receivedmodulated second RF signal 52 and the corrected modulated second RFsignal 66 may include at least a part of the second signal portion ofthe received modulated first RF signal 50 and the first signal portionof the received modulated second RF signal 52.

One exemplary method of synchronization may include periodicallytransmitting synchronizing signals, which may be the first RF carriersignal 40 a and the second RF carrier signal 40 b. The first RF carriersignal 40 a and the second RF carrier signal 40 b may be transmitted bythe first transmitter 22 and the second transmitter 24, respectively.The first receiver 26 may receive the transmitted first RF carriersignal 40 a and output a received unmodulated first RF signal 50 a. Thesecond receiver 28 may receive the transmitted second RF carrier 40 band output a received unmodulated second RF signal 52 a. The receivedunmodulated first RF signal 50 a and the received unmodulated second RFsignal 52 a may be received as inputs to the synchronization signaldecoder 58.

The synchronization signal decoder 58 may recognize the synchronizationsignals and may develop polarization correction factors. Thepolarization correction factors may be inputs to the first polarizationcorrector 60 and the second polarization corrector 62. The firstpolarization corrector 60 may utilize the polarization correctionfactors to correct the received modulated first RF signal 50 to accountfor portions of the transmitted modulated second RF signal 46 receivedby the first receiver 26 leaving only, or substantially only, thecorrect transmitted modulated first RF signal 44 in the correctedmodulated first RF signal 64. The second polarization corrector 62 mayutilize the polarization correction factors to correct the receivedmodulated second RF signal 52 to account for portions of the transmittedRF signal 44 received by the second receiver 28 leaving only, orsubstantially only, the transmitted modulated second RF signal 46 in thecorrected modulated second RF signal 66.

To allow polarization corrections to be made, synchronization signalsmay be transmitted. The synchronization signal controller 56 may switchthe first switch 56 a and the second switch 56 b causing each of thefirst switch 56 a and the second switch 56 b to connect to groundcontacts 56 c, which, in turn, interrupts the transmission of themodulated first RF signal 44 and the modulated second RF signal 46. Thesynchronization signal decoder 58 may interpret such an interrupt in thetransmission as an RF synchronization signal indicating to thesynchronization signal decoder 58 that the information immediatelyfollowing the interrupt is to be used for synchronization, forgenerating the correction factors described above.

After a predetermined period of time, the synchronization signalcontroller 56 may switch the first switch 56 a to move the first switch56 a from the ground contact 56 c to a point where the first switch 56 ais in operable communication with the signal generator 16 while thesecond switch 56 b stays connected to ground contact 56 c. This causesthe first transmitter 22 to transmit the first RF carrier signal 40 a,which may be an unmodulated horizontally polarized free space RFreference signal at a maximum amplitude and a reference phase (i.e., azero-degree phase), while the second transmitter 24 may transmit nosignal. If the orientation of the first receiver 26 and second receiver28 match the orientation of the first transmitter 22 and the secondtransmitter 24, then the first receiver 26 may receive the firstsynchronization signal(e.g., the first RF carrier signal 40 a) and thesecond receiver 28 may receive no signal.

If the orientation of the first receiver 26 and second receiver 28 donot match the orientation of the first transmitter 22 and the secondtransmitter 24, then each of the first receiver 26 and second receiver28 may receive a portion of the first synchronization signal transmittedby the first transmitter 22. The output of the first receiver 26 (e.g.,the received unmodulated first RF signal 50 a), and the output of thesecond receiver 28 (e.g., the received unmodulated second RF signal 52a) may be fed to the synchronization signal decoder 58. In cases wherethe first transmitter 22 and the second transmitter 24 are aligned withthe first receiver 26 and the second receiver 28, the output of thesecond receiver 28 may be no signal.

The synchronization signal decoder 58 may determine if RF polarizationcorrection is needed. If RF polarization correction is not needed, thesynchronization signal decoder 58 may provide the first polarizationcorrector 60 and the second polarization corrector 62 no polarizationcorrection factors or polarization correction factors that cause thefirst polarization corrector 60 and the second polarization corrector 62to receive and output RF signals without affecting the signals.

If RF polarization correction is needed, the synchronization signaldecoder 58 may compute polarization correction factors for use by thefirst polarization corrector 60 and the second polarization corrector62. The synchronization signal decoder 58 may store the polarizationcorrection factors and may provide the polarization correction factorsto the first polarization corrector 60 and the second polarizationcorrector 62 continuously until another synchronization signal isdetected.

When the next RF synchronization signal is detected by thesynchronization signal decoder 58, new polarization correction factorsmay be computed to replace the previously stored polarization correctionfactors.

In another example, a second synchronization signal may be transmittedafter the first synchronization signal. In this scenario, aftertransmitting the first synchronization signal for a predetermined periodof time, the second synchronization signal (e.g., the second RF carriersignal 40 b) may be transmitted when the synchronization signalcontroller 56 switches the first switch 56 a to connect to groundcontact 56 c and switches the second switch 56 b from the ground contact56 c to a point where the second switch 56 b is in operablecommunication with the signal generator 16.

This causes the second transmitter 24 to transmit the secondsynchronization signal,(e.g., the second RF carrier signal 40 b), whichmay be an unmodulated vertically polarized free space RF referencesignal at a maximum amplitude and a reference phase (i.e., a zero-degreephase),while the first transmitter 22 may transmit no signal. Thissecond synchronization signal may be received by the receiver 28 andprocessed in a substantially similar manner as the first synchronizationsignal except that the polarization correction factors determined by thesynchronization signal decoder 58 may be based on the firstsynchronization signal and the second synchronization signal.

After transmitting the first synchronization signal (and the secondsynchronization signal, if transmitted)for an amount of time sufficientfor the synchronization signal decoder 58 to develop the polarizationcorrection factors, the synchronization controller 56 may endtransmission of the first synchronization signal (and the secondsynchronization signal, if transmitted) by causing the switches 56 a and56 b to connect the modulated first RF signal 44 to the firsttransmitter 22 and to connect the modulated second RF signal 46 to thesecond transmitter 24 thereby recommencing the data transmission.

As stated above, the received modulated first RF signal 50 and thereceived modulated second RF signal 52 may be fed as inputs to the firstpolarization corrector 60 and the second polarization corrector 62. Thefirst polarization corrector 60 and the second polarization corrector 62may correct, via polarization correction factors computed based on thesynchronization signal(s), the received modulated first RF signal 50 andthe received modulated second RF signal 52 to produce the correctedmodulated first RF signal 64 and the corrected modulated second RFsignal 66.

The horizontally polarized signal components of the corrected modulatedfirst RF signal 64 may be maximized while the vertically polarizedsignal components of the corrected modulated first RF signal 64 may beminimized. The vertically polarized signal components of the correctedmodulated second RF signal 66 may be maximized while the horizontallypolarized signal components of the corrected modulated second RF signal66 may be minimized. The corrected modulated first RF signal 64 and thecorrected modulated second RF signal 66 may be fed as inputs to thedemodulator 30.

Stated otherwise, the first polarization corrector 60 and the secondpolarization corrector 62 may be configured to correct the receivedmodulated first RF signal 50 and the received modulated second RF signal52, based on the reception of one or more synchronization signals withknown characteristics, as described above, to produce the correctedmodulated first RF signal 64 and the corrected modulated second RFsignal 66. The corrected modulated first RF signal 64 may include thefirst signal portion of the received modulated first RF signal 50 and atleast a part of the second signal portion of the received modulatedsecond RF signal 52(e.g., a minimal portion)while the correctedmodulated second RF signal 66 may include at least a part of the secondsignal portion of the received modulated first RF signal 50 and thefirst signal portion of the received modulated second RF signal 52(e.g., a minimal portion).

In another example, a periodically recurring data sequence may be usedas the synchronization signal. For example, the Hypertext TransferProtocol (HTTP) specifies that data may be sent in data packets, andeach data packet may start with the same defined sequence. This definedsequence may be used by the synchronization signal decoder 58 as thesynchronization signal. If no suitable data sequence exists in the datastream to be communicated, a synchronization sequence can be added tothe data stream periodically.

For example, the synchronization signal may be used as a start bit and astop bit with the received modulated first RF signal 50 to determinewhether any errors in the transmission have occurred. The portion of thesynchronization signal when there is no carrier signal transmitted maybe regarded as the stop bit and the portion of the synchronizationsignal where the horizontal reference signal, or vertical referencesignal, if present, is transmitted is regarded as the start bit.

The synchronization signal decoder 58 may receive the transmitted startbit, the stop bit, the received modulated first RF signal 50 and thereceived modulated second RF signal 52 to determine if there are anytransmission errors. In the event transmission errors are detected, thedata associated with the received modulated first RF signal 50 and thereceived modulated second RF signal 52 may be transmitted again and/orany other suitable actions may be taken to correct the errors.

As another example, the synchronization signal may be periodically sentas a timing signal generated from an external clock to ensure thetransmitters(e.g., 22 and 24)and the receivers(e.g., 26 and 28)aresynchronized with one another. Error detection techniques may beutilized to determine whether transmission errors occur, such as, forexample, using an error-detecting code that is checked by thetransmission side and the receive side of the data communicator 200. Iferrors are detected, the data associated with the received modulatedfirst RF signal 50 and the received modulated second RF signal 52 may betransmitted again and/or any other suitable actions may be taken tocorrect the errors.

FIG. 3A illustrates a flow diagram for an exemplary method 300 fordecoding a synchronization signal in accordance with the presentdisclosure. In this example, the method 300 may utilize digital signalprocessing techniques to decode the synchronizing signal, and, as such,the portions of the synchronizing signal received by the first receiver26 and the second receiver 28 may be digitized coherently with oneanother. Stated otherwise, the first receiver 26 and the second receiver28 may utilize an analog-to-digital converter (ADC) to digitize thereceived portions of the synchronizing signal where the ADC of the firstreceiver 26 may be clocked simultaneously with the ADC of the secondreceiver 28 such that individual data samples may be paired. This mayallow a voltage sample from the first receiver 26 to be taken at thesame time as the corresponding sample from the second receiver 28 at anyinstant in time. Further, to decode the signal, an angular orientation Øof the first receiver 26 and the second receiver 28 may need to bedetermined as described below.

At 302, the method 300 may receive at least a portion of thesynchronization signal (i.e., an unmodulated horizontally polarized freespace RF reference signal at a maximum amplitude and a reference phase(i.e., a zero-degree phase))at the first receiver 26 and the secondreceiver 28. While this example has described the second receiver 28 asreceiving at least a portion of the synchronization signal, this is notalways the case. If the first receiver 26 and the second receiver 28 areproperly oriented with respect to the first transmitter 22 and thesecond transmitter 24, respectively, (i.e., the spatial polarizationaxes are aligned), only the first receiver 26 (e.g., the horizontallypolarized receiver) may receive the synchronization signal to be outputas a received first RF signal. If the spatial polarization axes of thefirst receiver 26 and the second receiver 28 are not properly orientedwith respect to the first transmitter 22 and the second transmitter 24(i.e., the spatial polarization axes are not aligned and the angle ofrotation of the misalignment may be represented by the angularorientation Φ), the first receiver 26 and the second receiver 28 mayreceive portions of the synchronization signal to be output as areceived first RF signal and a received second RF signal.

At 304, the method 300 may determine the angular orientation 0 of thefirst receiver 26 and the second receiver 28 with respect to the firsttransmitter 22 and the second transmitter 24, respectively. For example,the method 300 may detect, via an RF peak voltage detector, a peakvoltage Vhpk of the received unmodulated first RF signal output by thefirst receiver 26 and a peak voltage Vvpk of the received unmodulatedsecond RF signal output by the second receiver 28. If the peak voltagesVhpk and Vvpk are detected, the received modulated first RF signal 50and the received modulated second RF signal 52 are not beingtransmitted, and the method 300 may enter a synchronization mode. Theangular orientation 0 may be determined according to the followingequation:

$\begin{matrix}{\varnothing = {{ARCTAN}\left( \frac{y}{x} \right)}} & {{Equation}(1)}\end{matrix}$Where y is the peak voltage Vvpk of the second receiver 28 and x is thepeak voltage Vhpk of the first receiver 26.

At 306, the method 300 may correct the received unmodulated first RFsignal and the received unmodulated second RF signal to produce acorrected first unmodulated RF signal and a corrected unmodulated secondRF signal. The method 300 may accomplish this by determiningpolarization correction factors according to the following equations:x′=x cos Ø+y sin Ø  Equation (3),andy′=−x(sin Ø)+y cos Ø  Equation (4)where x is the received unmodulated first RF signal, y is the is thereceived unmodulated second RF signal, x′ is the corrected unmodulatedfirst RF signal and y′ is the corrected unmodulated second RF signal.

FIG. 3B illustrates a flow diagram for an exemplary method 310 fordetecting and decoding a synchronization signal in accordance with thepresent disclosure. At 312, the method 310 may receive a horizontalreceiver signal (e.g., a received unmodulated first RF signal includinga portion of the synchronization signal).At 314, the method 310 mayreceive a vertical receiver signal (e.g., a received unmodulated secondRF signal including a portion of the synchronization signal). At 316,the method 310 may detect, via an RF peak voltage detector, a peakvoltage Vhpk of the horizontal receiver signal. At 318, the method 210may detect, via the RF peak voltage detector, a peak voltage Vvpk of thevertical receiver signal. At 320, the method 310 may determine whetherno data signals are present and whether both peak voltages Vhpk and Vvpkare detected. If yes at 320, at 322, the method 310 may determinewhether the method 310 is currently in synchronization mode. If yes at322, at 324, the method 310 may stay in synchronization mode. If no at322, at 326, the method may enter synchronization mode. At 328, themethod 310 may calculate the angular orientation 0 of the first receiverand the second receiver. At 330, the method 310 may calculate thepolarization correction factors according to the following equations:Kx=sin Ø  Equation (5),andKy=cos Ø  Equation (6)where Kx is a horizontal polarization correction factor, Ky is avertical polarization correction factor, and Ø is the respective angularorientation of the horizontally polarized receiver and the verticallypolarized receiver, respectively.

At 332, the method 310 may determine whether previous polarizationfactors are being stored in a storage register. If yes at 332, at 334,the method 310 may clear the previous polarization correction factorsfrom the storage register. At 336, the method 310 may store the newpolarization correction factors. At 338, the method 310 may output thepolarization correction factors. If no at 332, at 340, the method 310may store the new polarization correction factors in the storageregister and proceed to 338.

If no at 320, at 342, the method 310 may determine that both datasignals are present and both Vhpk and Vvpk are present. At 344, themethod 310 may determine whether the method 310 is currently in datamode. If yes at 344, at 346, the method 310 may stay in data mode. At348, the method 310 may determine whether polarization factors arestored in the storage register. If yes at 348, the method 310 mayproceed to 338.

If no at 344 (not yet in data mode), the method 310 may enter data modeat 347 and proceed to 348 to determine whether polarization factors arestored in the storage register. If no at 348, the method 310 may returnto the beginning of the method 310 and the method 310 may be iterated asneeded.

FIG. 3C illustrates a flow diagram of an exemplary method 350 forcorrecting horizontal polarization and vertical polarization viapolarization correction. At 352, the method 350 may receive the receivedmodulated first RF signal (e.g., the signal received from the firstreceiver 26, which may be horizontally polarized) and the receivedmodulated second RF signal (e.g., the signal received from the secondreceiver 28, which may be vertically polarized). At 354, the method 350may retrieve a first polarization correction factor (e.g., a horizontalpolarization correction factor) and a second polarization factor (e.g.,a vertical polarization correction factor). At 356, the method 350 maygenerate a received corrected modulated first RF signal (e.g., thesignal having horizontal polarization) according to the followingequation:Vh=(Vx×Ky)+(Vy×Kx)   Equation (7),where Vx is the received modulated first RF signal, Vy is the receivedmodulated second RF signal, Kx is the horizontal polarization correctionfactor, and Ky is the vertical polarization correction factor. At 358,the method 350 may generate a received corrected modulated second RFsignal (e.g., the signal having vertical polarization) according to thefollowing equation:Vv=(Vx×Kx)−(Vx×Ky)   Equation (8),where Vx is the received modulated first RF signal, Vy is the receivedmodulated second RF signal, Kx is the horizontal polarization correctionfactor, and Ky is the vertical polarization correction factor.

The synchronization signal may be transmitted periodically such that theangular orientation Ø of each of the first receiver 26 and the secondreceiver 28 with respect to the first transmitter 22 and the secondtransmitter 24 may be determined periodically. For example, thesynchronization signal may be periodically transmitted such that theangular orientation Ø of the first receiver 26 and the second receiver28 with respect to the first transmitter 22 and the second transmitter24 do not change significantly between synchronization signaltransmissions.

To summarize, when a synchronization signal is received by the tworeceiving antennas 26 and 28, the angular orientation Ø may becalculated, the polarization correction factors necessary to correct thetwo received unmodulated RF signals may be calculated and stored forpolarization axis correction, and the polarization correction factorsmay be used to correct all subsequent received signals, extracting theoriginally transmitted horizontal and vertical signals. The correctedhorizontal and vertical signals may then be fed to the demodulators. Thepolarization correction factors may be used repeatedly until the nextsynchronization signal is received and the synchronization process maybe repeated.

In another example, a second synchronization signal (i.e., theunmodulated vertically polarized free space RF reference signal at amaximum amplitude and a reference phase (e.g., zero degrees)) may betransmitted immediately after the first synchronization signal (i.e.,the unmodulated horizontally polarized free space RF reference signal ata maximum amplitude and a reference phase (e.g., zero degrees)). Assuch, there may be four transmitter states including a transmit datastate, a transmit nothing state (e.g., no data transmission and nosynchronization signal transmission), a transmit first synchronizationsignal state, and a transmit second synchronization signal state.

In another example, two unmodulated carrier signals may be transmittedfor relatively short periods of time where one carrier signal may behorizontally polarized, and the other carrier signal may be verticallypolarized. If the receivers are not aligned with the respectivetransmitters, each receiving antenna may intercept a portion of thehorizontally polarized carrier signal and the vertically polarizedcarrier signal transmitted by the transmitting antennas.

For example, if one of the transmitting antennas transmits ahorizontally polarized signal at full amplitude and reference phase asthe first synchronization signal (e.g., a briefly transmittedsynchronization signal), each of the receiving antennas may have anoutput. By selecting the receiving antenna having a greater amount ofoutput as the receiving antenna to be used as the horizontally polarizedreceiving antenna, the output of the other receiving antenna may beregarded as an error signal. The error signal output by the otherreceiving antenna (i.e., the vertically polarized antenna)may be reducedto zero by multiplying an inverted portion of the signal output by thehorizontally polarized receiving antenna by the error signal. Similarly,when the second synchronization signal (i.e., a vertically polarizedsignal at full amplitude and reference phase) is transmitted, the errorsignal associated with the horizontally polarized receiving antenna maybe canceled out in a similar manner.

In this example, the axis rotation correction process may be performedoften enough so that any movement of the transmitter antennas or thereceiving antennas do not cause the received angle to changesignificantly while the error correction is being used.

To provide a computational example, a single horizontally polarizedsynchronization signal may be transmitted such that an amplitude of thesignal received by the horizontally polarized receiver is 1 volt (i.e.,1=x=horizontal amplitude), an amplitude of the signal received by thevertically polarized receiver is 0 volts (i.e., 0=y=vertical amplitude).The transmission path loss is 0 decibels (dB). The expected horizontalantenna voltage is 0.866025 volts, the expected vertical antenna voltageis 0.5 volts, and the misalignment angle calculated from the antennavoltages is 30 degrees. The correction factors, calculated from thetransmitted horizontally polarized synchronization signal, are0.866025=Kx and 0.5=Ky. The corrected horizontal output voltage is 1volt, and the corrected vertical antenna output voltage is 0.

In this example, the transmit data includes the following data: 0.5volts=x=horizontal amplitude, 0.75 volts=y=vertical amplitude, aresulting vector magnitude=0.901388, and a resulting vector angle is56.30993 degrees. The RF propagation through free space includes 0 dBtransmission path loss and an antenna misalignment angle of 30 degrees.The orthogonal receivers include the following data: 0.058013=expectedhorizontal antenna voltage, 0.899519=expected vertical antenna voltage,0.901388=received vector magnitude, and 86.30993=received vector anglecalculated from the antenna voltages. The polarization correctionfactors include the following data: 0.866025=Kxh, 0.5=Kyh, 0.866025=Kxv,and 0.5=Kyv. The corrected horizontal antenna output voltage is 0.5volts and the corrected vertical antenna output voltage is 0.75 volts.

To provide another computational example, a horizontally polarizedsynchronization signal and a vertically polarized synchronization signalmay be transmitted. With respect to the horizontally polarizedsynchronization signal, an amplitude of the signal received by thehorizontally polarized receiver is 1 volt (i.e., 1=x=horizontalamplitude), an amplitude of the signal received by the verticallypolarized receiver is 0 volts (i.e., 0=y=vertical amplitude), aresulting vector magnitude is 1, and a resulting vector angle is 0degrees. The transmission path loss is 0 decibels (dBs) and the axisorientation misalignment angle is 30 degrees. The expected horizontalantenna voltage is 0.866025 volts, the expected vertical antenna voltageis 0.5 volts, the received vector magnitude is 1, and the receivedvector angle calculated from the voltages is 30 degrees. The correctionfactors, calculated from the transmitted horizontally polarizedsynchronization signal, are 0.866025=Kxh and 0.5=Kyh.

With respect to the vertically polarized synchronization signal, anamplitude of the signal received by the horizontally polarized receiveris 0 volts (i.e., 0=x=horizontal amplitude), an amplitude of the signalreceived by the vertically polarized receiver is 1 volt (i.e.,1=y=vertical amplitude), a resulting vector magnitude is 1, and aresulting vector angle is 90 degrees. The transmission path loss is 0decibels (dBs), and the axis orientation misalignment angle is 30degrees. The expected horizontal antenna voltage is −0.5 volts, theexpected vertical antenna voltage is 0.866025 volts, the received vectormagnitude is 1, a received vector angle calculated from the antennavoltages is −60 degrees, and a received rotation angle corrected for thevertically polarized synchronization signal is 30 degrees. Thecorrection factors, calculated from the transmitted vertically polarizedsynchronization signal, are 0.866025=Kxv and 0.5=Kyv.

In this example, the transmit data includes the following data: 0.5volts=x=horizontal amplitude, 0.75 volts=y=vertical amplitude, aresulting vector magnitude=0.901388, and a resulting vector angle is56.30993 degrees. The RF propagation through free space includes 0 dBtransmission path loss and an antenna misalignment angle of 30 degrees.The orthogonal receivers include the following data: 0.058013=expectedhorizontal antenna voltage, 0.899519=received vector magnitude, and86.3099=received vector angle calculated from the antenna voltages. Thepolarization correction factors include the following data:0.866025=Kxh, 0.5=Kyh, 0.866025=Kxv, and 0.5=Kyv. The correctedhorizontal antenna output voltage is 0.5 volts and the correctedvertical antenna output voltage is 0.75 volts.

While exemplary methods of synchronization have been described, anysuitable method of method of synchronization may be utilized includingasynchronous and synchronous synchronization techniques.

After the received modulated first RF signal 50 and the receivedmodulated second RF signal 52 are corrected to produce the correctedmodulated first RF signal 64 and the corrected modulated second RFsignal 66, the demodulator 30 may demodulate the corrected modulatedfirst RF signal 64 and the corrected modulated second RF signal 66 toextract the first portion of data of the data stream from the correctedmodulated first RF signal 64 and the second portion of data of the datastream from the corrected modulated second RF signal 66.

The demodulator 30 may include a combiner 30 a that combines the firstportion of data of the data stream extracted from the correctedmodulated first RF signal 64 and the second portion of the data of thedata stream extracted from the corrected modulated second RF signal 66to output a data stream 54 containing the data that was contained indata stream 34. The output data stream 54 may be fed as an input to theoutput source 32.

As such, one additional exemplary benefit of the data communicator 200is the ability to correct for misalignment between the polarizations ofthe transmitters(e.g., 22 and 24)and the receivers(e.g., 26 and 28)ofthe data communicator 200.

FIG. 3 illustrates a block diagram of another exemplary embodiment of adata communicator 300 for communicating a data stream through free spacewith differently polarized electromagnetic radiation over a free spacechannel. The data communicator 300 of FIG. 3 is substantially identicalto the data communicator 200 of FIG. 2 , with a few exceptions/changesas described further below.

More particularly, the data source 12 and the output source 32 may bedata registers and the first modulator 18 and the second modulator 20 ofthe data communicator 300 may be 16-state quadrature amplitudemodulators, which may also be referred to as 16-QAMs. The 16-QAMs 18 and20 may modulate two different carrier signals into the same bandwidth bygenerating an amplitude modulated signal based on two carrier signalshaving the same frequency and a phase difference of ninety degrees.Typically, a cosine carrier signal is referred to as an in-phasecomponent while a sine carrier signal is referred to as a quadraturecomponent. With 16-QAMs, four bits of data may be modulated onto theamplitude modulated carrier and may be represented as one of 16 possiblestates.

As such, the data communicator 300 may include a phase shift network 68configured to phase shift the first RF carrier signal 40 a and thesecond RF carrier signal 40 b such that they are in a quadraturerelationship with one another (e.g., the first RF carrier signal 40 amay have a phase shift of zero degrees and the second RF carrier signal40 b may have has a phase shift of ninety degrees) to be fed as inputsto the first modulator 18 and the second modulator 20.

On the receiving side of the data communicator 300, the demodulator 30of the data communicator 300 may utilize quadrature amplitudedemodulation techniques. The data communicator 300 may further include asecond demodulator 70 that may also utilize quadrature amplitudedemodulation techniques. The receiving side may further include a signalgenerator 72 and a phase shift network 74.

The data communicator 300 of FIG. 3 may operate substantially similar tothe data communicator 10 of FIG. 1 in combination with the datacommunicator 200 of FIG. 2 , with a few exceptions/changes as furtherdescribed below.

In the example of FIG. 3 , the data stream may be a data byte, whichcontains 8 bits. The data source 12 may provide the data stream (i.e.,the data byte) having a first bandwidth to the data separator 14. Thedata separator 14 may separate the input signal 34 into a first signal36 carrying a first portion of data of the data stream having a secondbandwidth and a second signal 38 carrying a second portion of data ofthe data stream having a third bandwidth. In this example, the firstportion of data of the data stream and the second portion of data of thedata stream may each contain 4 bits of the data byte. The firstbandwidth of the input signal 34 may be greater than each of the secondbandwidth of the first signal 36 and the third bandwidth of the secondsignal 38.

In this example, the signal generator 16 may generate a referencecarrier signal 39 that may be fed as an input to the phase shift network68. The phase shift network 68 may output the first RF carrier signal 40a and the second RF carrier signal 40 b, and, in this example, the firstRF carrier signal 40 a and the second RF carrier signal 40 b may be in aquadrature relationship to one another. The first RF carrier signal 40 aand the second RF carrier signal 40 b may each be fed as inputs to thefirst modulator 18 and the second modulator 20. The first modulator 18may modulate the first signal 36 onto the first RF carrier signal 40 aand the second RF carrier signal 40 b and may output a modulated firstRF signal 44. The second modulator 20 may modulate the second signal 38onto the first RF carrier signal 40 a and the second RF carrier signal40 b and may output a modulated second RF signal 46.

The modulated first RF signal 44 may be fed as an input to an amplifier76 to be amplified, if necessary. After leaving the amplifier 76, themodulated first RF signal 44 may be fed as an input to the firsttransmitter 22. The modulated second RF signal 46 may be fed as an inputto an amplifier 78 to be amplified, if necessary. After leaving theamplifier 78, the modulated second RF signal 46 may be fed as an inputto the second transmitter 24.

The first transmitter 24 may transmit the modulated first RF signal 44with a first polarization over a free space channel 48. The secondtransmitter 24 may transmit the modulated second RF signal 46 with asecond polarization that is different than the first polarization overthe free space channel 48. In some implementations, the firstpolarization may be horizontal, and the second polarization may bevertical, however, the first polarization and the second polarizationmay be any suitable polarizations.

The first receiver 26 may receive the transmitted modulated first RFsignal 44 having the first polarization and may output a receivedmodulated first RF signal 50. The second receiver 28 may receive thetransmitted modulated second RF signal 46 having the second polarizationand may output a received modulated second RF signal 52. In someimplementations, the first receiver 26 may be horizontally polarized andthe second receiver 28 may be vertically polarized, however, the firstreceiver 26 and the second receiver 28 may be polarized in any suitablemanner.

The received modulated first RF signal 50 may be fed as an input to anamplifier 80 to be amplified, if necessary. Likewise, the receivedmodulated second RF signal 52 may be fed to an amplifier 82 to beamplified, if necessary. After the received modulated first RF signal 50leaves the amplifier 80, and after the received modulated second RFsignal 52 leaves the amplifier 82, the received modulated first RFsignal 50 and the received modulated second RF signal 52 may beprocessed without corrections.

Stated otherwise, if the polarization of the first transmitter 22matches the polarization of the first receiver 26 and the polarizationof the second transmitter 24 matches the polarization of the secondreceiver 28, no corrections may need to be made to the receivedmodulated first RF signal 50 and the received modulated second RF signal52 before being fed as inputs to the demodulator 30.

In contrast, if the polarization of the first transmitter 22 does notmatch the polarization of the first receiver 26 and/or the polarizationof the second transmitter 24 does not match the polarization of thesecond receiver 28, corrections may need to be made to the receivedmodulated first RF signal 50 and the received modulated second RF signal52 before being fed as inputs to the demodulator 30.

For exemplary purposes, in the example of FIG. 3 , it is to be assumedthat the polarization of the first transmitter 22 does not match thepolarization of the first receiver 26, and the polarization of thesecond transmitter 24 does not match the polarization of the secondreceiver 28. In this case, the received modulated first RF signal 50 andthe received modulated second RF signal 52 may need to be corrected, viathe first polarization corrector 60 and the second polarizationcorrector 62, such that a corrected modulated first RF signal 64 and acorrected modulated second RF signal 66 may each represent only one, orsubstantially only one, type of polarization before being fed as inputsto the demodulator 30 and the second demodulator 70.

With continued reference to FIG. 3 , the signal generator 72, which maybe synchronized and phase locked with the signal generator 16 on thetransmitter side of the data communicator 300, may generate a referencecarrier signal 73 that may be fed as an input to the phase shift network74. The phase shift network 74 may output a demodulating first RFcarrier signal 84 and a demodulating second RF carrier signal 85, and,in this example, the demodulating first RF carrier signal 84 and thedemodulating second RF carrier signal 85 may be in a quadraturerelationship to one another.

The demodulating first RF carrier signal 84, the demodulating second RFcarrier signal 85, and the corrected modulated first RF signal 64 mayeach be fed as inputs to the demodulator 30. The demodulator 30 may usethe demodulating first RF signal 84 and the demodulating second RFcarrier signal 85 to demodulate the corrected modulated first RF signal64 to extract the first portion of data of the data stream (i.e., 4bits) from the corrected modulated first RF signal 64.

The demodulating first RF carrier signal 84, the demodulating second RFcarrier signal 85, and the corrected modulated second RF signal 64 mayeach be fed as inputs to the second demodulator 70. The seconddemodulator 70 may use the demodulating first RF signal 84 and thedemodulating second RF carrier signal 85 to demodulate the correctedmodulated second RF signal 66 to extract the second portion of data ofthe data stream (i.e., 4 bits) from the corrected modulated second RFsignal 66. The demodulator 30 may output a data stream 86 containing thefirst portion of data of the data stream, which may be fed as an inputto the output source 32. The second demodulator 70 may output a datastream 88 containing the second portion of data of the data stream,which may be fed as an input to the output source 32.

While the examples in FIG. 1 , FIG. 2 , and FIG. 3 were directedprimarily to analog circuitry, an example provided below may incorporatedigital signal processing techniques.

FIG. 4 illustrates a block diagram of another exemplary embodiment of adata communicator 400 for communicating a data stream through free spacewith differently polarized electromagnetic radiation over a free spacechannel. The data communicator 400 may include a first digital signalprocessor (DSP) 402, a second DSP 404, a first digital-to-analogconverter (DAC) 406, a second DAC 408, a first amplifier 410, a secondamplifier 412, a first transmitter 414, a second transmitter 416, afirst signal generator 418, a second signal generator 420, a firstreceiver 422, a second receiver 424, a third amplifier 426, a fourthamplifier 428, a first ADC 430, a second ADC 432, a data source 434, andan output source 436.

The data source 434 may provide a data stream 438 (e.g., a byte) to thefirst DSP 402. The first DSP 402 may process the data stream 438 togenerate a first digital data stream 440 and a second digital datastream 442. The first digital data stream 440 may be fed as an input tothe first DAC 406, and the second digital data stream 442 may be fed asan input to the second DAC 408. The first DAC 406 may convert the firstdigital data stream 440 into a modulated first RF signal 444 and thesecond DAC 408 may convert the second digital data stream 442 to amodulated second RF signal 446.

The modulated first RF signal 444 may be fed as an input to the firstamplifier 410 to be amplified, if necessary. The modulated second RFsignal 446 may be fed as an input to the second amplifier 412 to beamplified, if necessary.

The modulated first RF signal 444 may be fed as an input to the firsttransmitter 414 and the modulated second RF signal 446 may be fed as aninput to the second transmitter 416. The first transmitter 414 maytransmit the modulated first RF signal 444 with a first polarizationover a free space channel 448. The second transmitter 416 may transmitthe modulated second RF signal 446 with a second polarization that isdifferent than the first polarization through the free space channel448. In some implementations, the first polarization may be horizontal,and the second polarization may be vertical, however, the firstpolarization and the second polarization may be any suitablepolarizations.

The first receiver 422 may receive the transmitted modulated first RFsignal 444 having the first polarization and may output a receivedmodulated first RF signal 450. The second receiver 424 may receive thetransmitted modulated second RF signal 446 having the secondpolarization and may output a received modulated second RF signal 452.In some implementations, the first receiver 422 may be horizontallypolarized and the second receiver 424 may be vertically polarized,however, the first receiver 422 and the second receiver 424 may bepolarized in any suitable manner.

The received modulated first RF signal 423 may be fed as an input to thethird amplifier 426 to be amplified, if necessary. The output 450 of theamplifier 426 drives the first ADC 430. The received modulated second RFsignal 425 may be fed as an input to the fourth amplifier 428 to beamplified, if necessary. The output 452 of the amplifier 428 drives thesecond ADC 432.

The first ADC 430 may digitize the amplified modulated first RF signal450 to generate first digital output data 454. The second ADC 432 maydigitize the amplified modulated second RF signal 452 to generate seconddigital output data 456.

The second signal generator 420 may provide clocking signals to thefirst ADC 430, the second ADC 432, and the second DSP 404. The firstdigital output data 454 and the second digital output data 456 may befed as inputs to a receive side of the second DSP 404. The second DSP404 may demodulate the first digital output data 454 and the seconddigital output data 456 and may output an output data stream 458 to befed as an input to the output source 436. A received data outputregister on the receive side of the second DSP 404 may be updated withthe received first digital data output 454 and the second digital dataoutput 456 at a rate associated with a symbol clock.

In the event an allocated RF channel used is at a frequency higher thanthe capabilities of either the analog system (e.g., the examples of FIG.1 , FIG. 2 , and FIG. 3 ) or the DSP system (e.g., the example of FIG. 4), an upconverter (not shown) may be utilized on the transmit sidebefore the signals are transmitted and a downconverter may be utilizedon the receive side after the signals have been received to allow signalprocessing operations of the data communicators 10, 200, 300, and 400 tooccur at a lower frequency, which also may ease circuit designrequirements.

While some of the examples have described using 16-QAM modulation andits associated demodulation techniques, it is to be understood that themodulation/demodulation techniques associated with the presentapplication are not limited to 16-QAM, and any suitablemodulation/demodulation techniques may be utilized. It should be notedthat while the present disclosure has described polarizations as beinghorizontal and vertical relative to one another, it is to be understoodthat any suitable polarizations may be utilized, such as, for exampleany two polarizations that are orthogonal to one another.

FIG. 5 illustrates a flow diagram for an exemplary method 500 forcommunicating a data stream through free space with differentlypolarized electromagnetic radiation over a free space channel. At 505,the method 500 may include receiving input data stream having a firstbandwidth. At 510, the method 500 may separate the input data streaminto a first signal carrying a first portion of data of the data streamhaving a second bandwidth and a second signal carrying a second portionof data of the data stream having a third bandwidth. The first bandwidthof the input signal may be greater than each of the second bandwidth ofthe first signal and the third bandwidth of the second signal. In someimplementations, the first portion of data of the data stream may be aninitial portion and the second portion of data of the data stream may bea remaining portion such that the entire data stream is communicated by,at least in part, the first signal and the second signal.

At 515, the method 500 may include generating a first RF carrier signaland a second RF carrier signal. At 520, the method 500 may includemodulating the first signal onto the first RF carrier signal to output amodulated first RF signal and modulating the second signal onto thesecond RF carrier signal to output a modulated second RF signal.

At 525, the method 500 may include transmitting the modulated first RFsignal with a first polarization over a free space channel andtransmitting the modulated second RF signal with a second polarizationthat is different than the first polarization through the free spacechannel. In some implementations, the first polarization may behorizontal, and the second polarization may be vertical, however, thefirst polarization and the second polarization may be any suitablepolarizations.

At 530, the method 500 may include receiving the transmitted modulatedfirst RF signal having the first polarization to output a receivedmodulated first RF signal and receiving the transmitted modulated secondRF signal having the second polarization to output a received modulatedsecond RF signal. In some implementations, the receivers may bepolarized horizontally and/or vertically polarized.

At 535, the method 500 may branch into two paths as follows: if thepolarization of the transmitters and receivers utilized by the method500 match (e.g., are aligned), the method 500 may include demodulatingthe received modulated first RF signal and demodulating the receivedmodulated second RF signal to extract the first portion of data of thedata stream from the received modulated first RF signal and the secondportion of the data of the data stream from the received modulatedsecond RF signal to be recombined; and, if the polarization of thetransmitters and receivers utilized by the method 500 do not match(e.g., are misaligned), the method 500 may include correcting thereceived modulated first RF signal via a first polarization correctorand correcting the received modulated second RF signal via a secondpolarization corrector via one or more synchronization signals anddemodulating the corrected modulated first RF signal and/or thecorrected modulated second RF signal to extract the first portion ofdata of the data stream from the corrected modulated first RF signal andthe second portion of data of the data stream from the transformedmodulated second RF signal to be recombined.

It is to be understood that the method 500 may be modified to includeother analog and/or digital signal processing techniques, such as, forexample, QAM processing techniques other than 16-QAM processingtechniques. To accomplish this, the method 500 may include, on thetransmit side, generating and/or phase shifting two carrier signals tobe fed to two separate QAMs and modulating the signals carrying theportions of data of the data stream onto the carrier signals of the QAMsto be transmitted, and, on the receive side, generating and/or phaseshifting two demodulating RF signals, synchronized with transmit side,to be fed to two separate demodulating QAMs, and demodulating thesignals to extract the portions of data of the data stream from thesignals to be recombined.

While FIGS. 3A, 3B, 3C, and 5 illustrate various actions occurring inserial, it is to be appreciated that various actions illustrated couldoccur substantially in parallel, and while actions may be shownoccurring in parallel, it is to be appreciated that these actions couldoccur substantially in series. While a number of processes are describedin relation to the illustrated methods, it is to be appreciated that agreater or lesser number of processes could be employed and thatlightweight processes, regular processes, threads, and other approachescould be employed. It is to be appreciated that other example methodsmay, in some cases, also include actions that occur substantially inparallel. The illustrated exemplary methods and other embodiments mayoperate in real-time, faster than real-time in a software or hardware orhybrid software/hardware implementation, or slower than real time in asoftware or hardware or hybrid software/hardware implementation.

While for purposes of simplicity of explanation, the illustratedmethodologies are shown and described as a series of blocks, it is to beappreciated that the methodologies are not limited by the order of theblocks, as some blocks can occur in different orders or concurrentlywith other blocks from that shown and described. Moreover, less than allthe illustrated blocks may be required to implement an examplemethodology. Furthermore, additional methodologies, alternativemethodologies, or both can employ additional blocks, not illustrated.

In the flow diagram, blocks denote “processing blocks” that may beimplemented with logic. The processing blocks may represent a methodstep or an apparatus element for performing the method step. The flowdiagrams do not depict syntax for any particular programming language,methodology, or style (e.g., procedural, object-oriented). Rather, theflow diagram illustrates functional information one skilled in the artmay employ to develop logic to perform the illustrated processing. Itwill be appreciated that in some examples, program elements liketemporary variables, routine loops, and so on, are not shown. It will befurther appreciated that electronic and software applications mayinvolve dynamic and flexible processes so that the illustrated blockscan be performed in other sequences that are different from those shownor that blocks may be combined or separated into multiple components. Itwill be appreciated that the processes may be implemented using variousprogramming approaches like machine language, procedural, objectoriented or artificial intelligence techniques.

FIG. 6 illustrates a block diagram of an exemplary machine 600 forcommunicating a data stream through free space with differentlypolarized electromagnetic radiation over a free space channel. Themachine 600 includes a processor 602, a memory 604, I/O Ports 610, and afile system 612 operably connected by a bus 608.

In one example, the machine 600 may transmit input and output signalsdescribed above via, for example, I/O Ports 610 or I/O Interfaces 618.The machine 600 may also include the data communicators 10, 200, 300,and 400, and all of their associated components. Thus, datacommunicators 10, 200, 300, and 400, and their associated components maybe implemented in machine 600 as hardware, firmware, software, orcombinations thereof and, thus, the machine 600 and its components mayprovide means for performing functions described herein as performed bythe data communicators 10, 200, 300, and 400 and their associatedcomponents.

The processor 602 can be a variety of various processors including dualmicroprocessor and other multi-processor architectures. The memory 604can include volatile memory or non-volatile memory. The non-volatilememory can include, but is not limited to, ROM, PROM, EPROM, EEPROM, andthe like. Volatile memory can include, for example, RAM, synchronous RAM(SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rateSDRAM (DDR SDRAM), and direct RAM bus RAM (DRRAM).

A disk 606 may be operably connected to the machine 600 via, forexample, an I/O Interface (e.g., card, device) 618 and an I/O Port 610.The disk 606 can include, but is not limited to, devices like a magneticdisk drive, a solid-state disk drive, a floppy disk drive, a tape drive,a Zip drive, a flash memory card, or a memory stick. Furthermore, thedisk 406 can include optical drives like a CD-ROM, a CD recordable drive(CD-R drive), a CD rewriteable drive (CD-RW drive), or a digital videoROM drive (DVD ROM). The memory 604 can store processes 614 or data 616,for example. The disk 606 or memory 604 can store an operating systemthat controls and allocates resources of the machine 600.

The bus 608 can be a single internal bus interconnect architecture orother bus or mesh architectures. While a single bus is illustrated, itis to be appreciated that machine 600 may communicate with variousdevices, logics, and peripherals using other busses that are notillustrated (e.g., PCIE, SATA, Infiniband, 1394, USB, Ethernet). The bus608 can be of a variety of types including, but not limited to, a memorybus or memory controller, a peripheral bus or external bus, a crossbarswitch, or a local bus. The local bus can be of varieties including, butnot limited to, an industrial standard architecture (ISA) bus, amicrochannel architecture (MCA) bus, an extended ISA (EISA) bus, aperipheral component interconnect (PCI) bus, a universal serial (USB)bus, and a small computer systems interface (SCSI) bus.

The machine 600 may interact with input/output devices via I/OInterfaces 618 and I/O Ports 610. Input/output devices can include, butare not limited to, a keyboard, a microphone, a pointing and selectiondevice, cameras, video cards, displays, disk 606, network devices 620,and the like. The I/O Ports 610 can include but are not limited to,serial ports, parallel ports, and USB ports.

The machine 600 can operate in a network environment and thus may beconnected to network devices 620 via the I/O Interfaces 618, or the I/OPorts 610. Through the network devices 620, the machine 600 may interactwith a network. Through the network, the machine 600 may be logicallyconnected to remote devices. The networks with which the machine 600 mayinteract include, but are not limited to, a local area network (LAN), awide area network (WAN), and other networks. The network devices 620 canconnect to LAN technologies including, but not limited to, fiberdistributed data interface (FDDI), copper distributed data interface(CDDI), Ethernet (IEEE 802.3), token ring (IEEE 802.5), wirelesscomputer communication (IEEE 802.11), Bluetooth (IEEE 802.15.1), Zigbee(IEEE 802.15.4) and the like. Similarly, the network devices 620 canconnect to WAN technologies including, but not limited to, point topoint links, circuit switching networks like integrated services digitalnetworks (ISDN), packet switching networks, and digital subscriber lines(DSL). While individual network types are described, it is to beappreciated that communications via, over, or through a network mayinclude combinations and mixtures of communications.

While example systems, methods, and so on, have been illustrated bydescribing examples, and while the examples have been described inconsiderable detail, it is not the intention of the applicant torestrict or in any way limit scope to such detail. It is, of course, notpossible to describe every conceivable combination of components ormethodologies for purposes of describing the systems, methods, and soon, described herein. Additional advantages and modifications willreadily appear to those skilled in the art. Therefore, the invention isnot limited to the specific details, the representative apparatus, andillustrative examples shown and described. Thus, this application isintended to embrace alterations, modifications, and variations that fallwithin the scope of the appended claims. Furthermore, the precedingdescription is not meant to limit the scope of the invention. Rather,the scope of the invention is to be determined by the appended claimsand their equivalents.

To the extent that the term “includes” or “including” is employed in thedetailed description or the claims, it is intended to be inclusive in amanner similar to the term “comprising” as that term is interpreted whenemployed as a transitional word in a claim. Furthermore, to the extentthat the term “or” is employed in the detailed description or claims(e.g., A or B) it is intended to mean “A or B or both”. When theapplicants intend to indicate “only A or B but not both” then the term“only A or B but not both” will be employed. Thus, use of the term “or”herein is the inclusive, and not the exclusive use. See, Bryan A.Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995).

What is claimed is:
 1. A machine or group of machines for transmittinginformation, comprising: a data separator configured to separate a datasignal received into a first signal and a second signal such that thefirst signal includes a first portion of data of the data signal and thesecond signal includes a second portion of data of the data signal; oneor more modulators configured to: modulate a first carrier signal withthe first signal to produce a modulated first signal; and modulate asecond carrier signal with the second signal to produce a modulatedsecond signal; one or more transmitters configured to: radiate themodulated first signal with a first polarization as a polarized firstsignal over a free space channel; and radiate the modulated secondsignal with a second polarization as a polarized second signal throughthe free space channel, wherein the first polarization is different fromthe second polarization; and a synchronization signal controllerconfigured to generate a synchronization signal different from themodulated first signal and the second modulated second signal, thesynchronization signal carries data that indicates at least one of (a)that the polarized first signal is polarized with the first polarizationas radiated by the one or more transmitters and (b) that the polarizedsecond signal is polarized with the second polarization as radiated bythe one or more transmitters.
 2. The machine or group of machines ofclaim 1, wherein the first polarization and the second polarization areorthogonal to one another.
 3. The machine or group of machines of claim1, wherein the first portion of the data of the data signal and thesecond portion of the data of the data signal are an entirety of thedata of the data signal.
 4. The machine or group of machines of claim 1,further comprising: a phase shift network configured to phase shift thefirst carrier signal and the second carrier signal such that the firstcarrier signal and the second carrier signal are in a quadraturerelationship to one another.
 5. The machine or group of machines ofclaim 4, wherein the one or more modulators utilize quadrature amplitudemodulation techniques.
 6. The machine or group of machines of claim 1,wherein the modulated first signal and the modulated second signal areradiated in a single radio frequency spectrum.
 7. The machine or groupof machines of claim 1, wherein the data signal has a first bandwidth,the modulated first signal has a second bandwidth, and the modulatedsecond signal has a third bandwidth; wherein the second bandwidth isless than the first bandwidth; and wherein the third bandwidth is lessthan the first bandwidth.
 8. A machine or group of machines forreceiving information, comprising: one or more receivers configured toreceive a polarized first signal and a polarized second signal, whereineach of the polarized first signal and the polarized second signalinclude a first signal portion and a second signal portion, wherein thefirst signal portion of the polarized first signal and the second signalportion of the polarized second signal are polarized with a firstpolarization and the second signal portion of the polarized first signaland the first signal portion of the polarized second signal arepolarized with a second polarization different from the firstpolarization, wherein the first signal portion of the polarized firstsignal and the second signal portion of the polarized second signalcommunicate a first portion of data of a data signal; wherein the secondsignal portion of the polarized first signal and the first signalportion of the polarized second signal communicate a second portion ofthe data of the data signal; a synchronization signal decoder configuredto receive the polarized first signal, the polarized second signal, anda synchronization signal that has stored therein information regardingpolarization of at least one of the received polarized first signal andthe received polarized second signal; one or more polarizationcorrectors configured to correct one or more of the polarized firstsignal and the polarized second into a corrected polarized first signalor a corrected polarized second signal, respectively, wherein thecorrected polarized first signal includes the first signal portion ofthe polarized first signal and at least a part of the second signalportion of the polarized second signal, and/or wherein the correctedpolarized second signal includes at least a part of the second signalportion of the polarized first signal and the first signal portion ofthe polarized second signal; one or more demodulators configured to:demodulate the corrected polarized first signal to provide a demodulatedfirst signal; wherein the demodulated first signal carries the firstportion of the data of the data signal; and demodulate the correctedpolarized second signal to provide a demodulated second signal; whereinthe demodulated second signal carries the second portion of the data ofthe data signal; and a combiner configured to combine the demodulatedfirst signal with the demodulated second signal to provide an outputsignal; wherein the output signal carries the data of the data signal.9. The machine or group of machines of claim 8, wherein the firstpolarization and the second polarization are orthogonal to one another.10. The machine or group of machines of claim 8, wherein thesynchronization signal is received by the one or more receivers beforethe polarized first signal and the polarized second signal are receivedby the one or more receivers.
 11. The machine or group of machines ofclaim 8, wherein the synchronization signal is a synchronoussynchronization signal.
 12. The machine or group of machines of claim 8,wherein the synchronization signal is an asynchronous synchronizationsignal.
 13. The machine or group of machines of claim 8, wherein thepolarized first signal and the polarized second signal are stored by theone or more polarization correctors after being received by the one ormore receivers; wherein the synchronization signal decoder is furtherconfigured to determine polarization correction factors associated withthe polarized first signal and the polarized second signal based, atleast in part, on the synchronization signal; and wherein the one ormore polarization correction factors are configured to correct thepolarized first signal and the polarized second signal based, at leastin part, on the polarization correction factors into the correctedpolarized first signal and the corrected polarized second signal. 14.The machine or group of machines of claim 13, wherein subsequentsynchronization signals are periodically received by the synchronizationsignal decoder.
 15. The machine or group of machines of claim 8, whereinthe at least the part of the second signal portion of the polarizedsecond signal is an entirety of the second signal portion of thepolarized second signal.
 16. The machine of claim 8, wherein the atleast the part of the first signal portion of the polarized first signalis an entirety of the first signal portion of the polarized firstsignal.
 17. The machine or group of machines of claim 8, wherein thefirst portion of the data of the data signal and the second portion ofthe data of the data signal are an entirety of the data of the datasignal.
 18. The machine or group of machines of claim 8, wherein thepolarized first signal and the polarized second signal are quadraturesignals; the machine or group of machines further comprising: a signalgenerator configured to generate a first demodulating signal and asecond demodulating signal; and a phase shift network configured tophase shift the first demodulating signal and the second demodulatingsignal such that the first demodulating signal and the seconddemodulating signal are in a quadrature relationship to one another;wherein the first demodulating signal and the second demodulating signalare fed to the one or more demodulators to demodulate the correctedpolarized first signal and the corrected polarized second signal. 19.The machine or group of machines of claim 8, wherein the polarized firstsignal and the polarized second signal are received from a single radiofrequency spectrum.
 20. The machine or group of machines of claim 8,wherein, before being received by the one or more receivers, the firstsignal portion of the polarized first signal and the second signalportion of the polarized first signal are polarized with the firstpolarization and the first signal portion of the polarized second signaland the second signal portion of the polarized second signal arepolarized with the second polarization.